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Hi fellows, I hope that everyone healthy,
I have a doubt about to input cost compositions with auxiliary cost compositions in Spider, can someone help me?
Look below, I have a cost composition for clear road side vegetation from estimate software that give $733.145,25 for 2.475.000m2, i.e. $0,30 / m2.
I tried to simulate the same composition in Spider using multi-resources because I thought that is better way, but unfortunately the value is different, $0,33/m2, $820.281,89, I expected it to be exactly the same, but not.
What my mistake? the way is different? is there a viable way forward?
My inttention is to fit a model to control budget and delivery dates for main resources of the project like truck, bulldozers and so on.
Thank you in advance and best regards for all,
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Daniel Morais
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Mr. Vladimir, you are right, I will do like this way, much better indeed.
Thank you,
Best Regards,
Daniel Morais
Daniel,
I don’t understand why do you plan to use space or material leveling for simulating equipment mobilization.
Spider Project models resource production at the moments or on activities when they become available and then these resources can be used on project activities.
So I don’t see the need for material leveling in this specific case. It can be used for modeling limited productivity of the asphalt plant but it does not make sense to use it for modeling of resource mobilization.
Hi Rafael,
The plannig won't be with this quantity, indeed is too much work for 1 bar only, my idea is only how example, to ilustrate my doubt.
The plan will be make dividing tranche by tranche according the volumes to be executed.
My doubt is about can to simulate the too close cost of services (according our bdget/estimate) versus the best histogram of main resources, because our project in into of a big plan that we have almost US$ 90MM of international equipaments acquisitions (Trucks, Bulldozers, asphalt plant, motorgrader and so on).
I will try to model and conciliate this costs X resources (histogram) X equipments mobilization, using Spatial Recources Technique, CHECK IN ( Purchase Order) >> lead time >> CHECK OUT (Equipment on site), then the activity can starts after this, using the RCP (Material leveling) on Spider.
So if I will be success, any change of equipment delivery on project the plan will change and we could knows the bottleneck easier and take appropriate action to solve the project delay.
Best Regards,
Daniel Morais
Hi Mr. Vladimir,
Thank you for your contribution.
I did understand the concepts and I consider my planning like a compass, to guide me for one direction too close of real situation.
I always would like to use referecence books in practice, can you share some example?
Best Regards,
Daniel Morais
Unit Price Contract | Practical Law
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At home most contractors use unit-price costing and productivity tracking to control construction project costs, no matter if the contract is fixed price or unit cost. Usually, in our jobs many activities share repetitive tasks that are easily measured so it makes sense to pay attention to unit costs spannig all acticvities that share repetitive tasks. Quantity is the glue that makes cost meaningful. Unit costs is what we use to price our fixed price as well as unit price bids. Cost per activity is of not much use for use for us for cost control, in any case of use for cash flow.
Perhaps it would help if a Unit Costing Table is made available. Here Spider should be able to track unit cost and unit production rates for repetitive tasks that span many activities. Fields could be as per columns on the suggested tables. The implementation is a challenge I believe Spider developers can overcome. At home we would still use our financial system but it can be an improvement for others who prefer unit costing within the scheduling tool.
Cost Loading in Spider Project is usually done using Reference-books.
If activity and resource types were defined then unit costs (usually contractual) can be assigned from the Reference-books, resource hour cost is taken from the Reference-book, resource assignment cost can be taken from the reference-book also if payment depends on the volume of work done.
Contractors usually manage two budgets - one is contractual based on contractual unit costs or fixed costs of project activities, the second is based on resource work cost with additional indirect cost component that is calculated by formula as some percent of the total expenses or the cost of workforce (depends on the company standards).
Using both budgets it is easy to understand what profit can be achieved.
Payments can be entered or imported from another tool to understand what amounts were done but still not paid. Payments are usually delayed and are done for completed activities, not just for volumes done. So Spider calculation of the cost of the work performed does not mean that the same sum will be paid. But it helps to undertsand who owns to whom and what amounts that can be helpful for contract management.
It is hard to believe the clearing of 2.5 million m2 does is not impacted and do not impact other activities. As per your schedule it takes 330 days, it is a very long duration activity.
If in between two road sections a bridge must be required to be built, a road contractor is not to delay the before and after road segments, he might work both segments at the same time the bridge is built, the clearing at both sides at the same time. I expect such situation to happen in a long road construction job.
* We do not cost load our schedule for cost control. We use our accounting system for unit job costing. Our estimators use unit costs, difficult or impossible to get meaningful unit cost with activity-based costing. As if not enough, distributing cost data among activities can be very challenging and time consuming; an everyday example can be the purchase and delivery of bricks where a single truckload is to be distributed among many activities, what a mess.
* While we do not cost load our schedules, unless at gunpoint, in such case cost loading should be done after the schedule activities and logic is approved. If latter on you have to split the activity into segments all cost distribution work will be lost.
* We do not cost load our schedules for payment purposes, it is crazier but shit happens. For scheduling hauling activities we use volume of work using loose measure but for payment of these activities BOQ cost codes and quantities must be in bank measure. Bank measure vs Loose measure is of concern, if difference is high someone might be stealing or soil properties data was wrong, in rare cases consolidation might be the cause.
OWN.718. The Great Divorce: Cost Loaded Schedule Updating - PDF Free Download
* We do not cost load our schedules for EVM, we do not use it unless at gunpoint.
(PDF) Earned value method as a tool for project control
* We only cost load our schedules in the rare case financial constraints are relevant. To my knowledge a function only Spider Project can tackle.
It makes all sense for your planning software to provide all cost functions, you never know when someone at the top of the food chain will require such cost loading.
Daniel,
if the results are the same as the spreadsheet I suppose it is good. I agree with Rafael, cost loading at the resource level is not worth it. I preffer to enter the activity budget, resorces, hour rates or volume rates of resources and compare the budget to the real estimated cost.
Best regards,
Bogdan
Too much details into cost loading might divert attention away from the schedule logic.
Road Construction is mostly driven by earthwork activities, but earthwork per segment is not a constant, distance to disposal area is not constant, progress in between stations is not constant. For some road segment cut-to-fill will require no howling for others it might, different segments with different howling distance will require different number of trucks.
Wise selection of planning segments is key for good planning. Earthwork information is on the Mass Diagram, if you miss it most probably the schedule will be wrong.
Because of the topsoil stripping area, without looking at the drawings, I expect it to be a relatively long road, requiring many road segments, with some bridges, some access and exit road segments.
Best Regards, Rafael
Hi Bogdan,
I founded one way, look my last post please if you understood and agree.
Thank you one more time,
Best regards,
Daniel Morais
Hi Rafael,
I thought use hammocks like you said, but the problem that I have many activities and maybe doesn't can be the best way. After make a reflexion, breath and burn some neurons and using yours tips, the best way founded was discover the relationship between Excel composition and Spider and uses the resource hours and production like base values to calc. Look below:
1. How we have a cascade calculus I made one formula stating by the main quantity, 2.475.000 m2;
2. On the first level I have one production of 750m2/h so, 2.475.000m2 / 750m2/h = 3.300h, all the services that we have from next level will have relationship with the 3.300h.
3. 2.475.000m2 x 0,15m3/m2 = 371.250 m3;
3. 371.250m3 / 180m3/h = 2.062,5 h
4. So 2.062,5h / 3.300h = 0,625, this is new workload to input on Spider.
5. Same way 3.639,71h / 3.300h = 1,103, how Spider doesn't accept workload bigger than 100, I changed quantity from 1 to 2 and New workload from 100 for 0,5515 so, 2 x 0,5515 = 1,103.
Thank you for your help,
Best Regards,
Daniel Morais
Daniel,
you need 2 formulas, one for number of resources, one for workload of resources.
I suggest you create a temporary user field in which you will copy-paste the total cost of resources, then you fill the number of resouces with 1 and load with 100 and perform schedule and cost calculations.
The formulas for number of resources should look like if (User field value/Cost component Value != 1, RoundUp(User field value/Cost component Value), 1).
Perform schedule and cost calculation again. The resulted costs should be higher than the costs for 1 resource with 100 load.
The second formula is for the workload and it should look like User field value/Cost component value. This should adjust the workload in order to set the cost at decimal value. However you may get workloads such as 23.42309432984320%.
This can work from a arithmetical point but it makes little scense from a resource loaded schedule...no resource will work 23.42309432984320% x 8h/day = 1.873847546387456 h.
Best regards,
Bogdan
Hi Bogdan,
I did understand what you said. The challenge is to find what the mathematics calculus for change all index of one time, for fit value on the sheet, because i have many many compositions like this.
Thank you,
Best regards,
Daniel Morais
Yes Mr. Vladimir,
You're right, but the three activities should performs together because after clear road side I will load the truck, transport for waste disposal area and on disposal area I will spread the organic materials, all services happen simultaneously.
I think that the index should be changed for fit with the spreadsheet, I will try.
Thank you,
Best regards,
Daniel Morais
COST LOADING AT THE RESOURCE LEVEL IS TOO GRANULAR
COST LOADING AT THE ACTIVITY LEVEL IS LESS GRANULAR
- But misses meaningful volumes of work when multiple volumes of work are to be considered.
BETTER IF USING A DRIVING PRODUCTIVITY TYPE ACTIVITY AND A FEW HAMMOCKS WHEN MULTIPLE VOLUMES OF WORK MUST BE CONSIDERED
- If you use separate activities the software might schedule the activities to happen at different times; to keep them together can be a nightmare, especially with multiple calendars and resource leveling.
- If using hammocks you can keep the activities to happen in sync. If resource leveling delays any hammock then the software will issue a warning for you to take care of the issue.
NOT CONSIDERING RESOURCES WHEN SCHEDULING WOULD BE NUTS BUT WE FIND USING CPM FOR JOB COSTING AS WELL AS FOR PAYMENT APPLICATIONS IS NOT A GOOD IDEA.
https://www.semanticscholar.org/paper/The-Great-Divorce%3A-Cost-Loaded-S...
- We find simplified cost loading for the purpose of financial resource constraining of much value, "no ticky, no laundry".
Daniel,
If you want to do it the way you did it you have to change workloads, look at resource assignment IEP017 under ”Spread and compactation in waste disposal area (Multi-Resource)”, if you change the workload to 12.50 then Spider and Excel numbers are the same.
Best regards,
Bogdan
Daniel,
it looks like initial data contains three activities with different volumes measured in different units (m2, m3) and productivity, and so with different duration.
You assigned all crews to one activity and used the productivity of only one crew.
I suspect that the work time of different crews is not the same.
733k Estimate
820k Model
87k diff
11.87% diff %
Average profit on construction jobs is less than 10%, this difference is unacceptable.
It is a single activity schedule, interesting if several hundred/thousands of activities, even more when updating actual values for comparison against budget.
Good Luck.
Email: PPadmin@planningplanet.com
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